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An aqueous two-phase system (ATPS) composed of PEG35000, Na2CO3, K2CO3, and their mixtures at 298 K was studied. The liquid–liquid equilibrium (LLE) of these systems, including binodal curves, tie-lines, tie-line length, and slope of the tie-line, were obtained. Additionally, for the first time, salt mixtures with different initial mass ratios of 1:3, 1:1, and 3:1 were used to prepare the aqueous two-phase systems. The effect of electrolyte and salting-out power for these systems was examined and compared. Consistent with the literature, it was found that the salting-out power of Na+ is higher than that of the K+ cation. Furthermore, in Na2CO3 and K2CO3 mixtures, increasing the amount of sodium ions resulted in stronger salting-out power. The LLE data was correlated with the Othmer-Tobias, Bancroft, and Setschenow models, and good agreement was found with all three models. [ABSTRACT FROM AUTHOR]

Three ionic liquids (ILs)(1-ethyl-2,3-dimethylimidazolium acetate, [EMMIM][AC]; tributyl-methylammonium acetate, [N4,4,4,1][AC]; and tetraethylammonium acetate, [N2,2,2,2][AC]) were chosen. The vapor–liquid equilibrium (VLE) data of ternary mixtures (acetate + ethanol + IL) were measured at 101.3 KPa. NRTL equation was used to correlate the data. From NRTL model, for [N2,2,2,2][AC], [EMMIM][AC], and [N4,4,4,1][AC], minimum mole fractions for completely eliminating azeotrope are 0.015, 0.020 and 0.022, respectively. From the average relative volatility and σ-profiles, it can be obtained that the separation ability order is [EMMIM][AC] > [N2,2,2,2][AC] > [N4,4,4,1][AC]. [ABSTRACT FROM AUTHOR]

The main purpose of this research was to evaluate the mass/volume percentage (%m/v) solubility of acetaminophen (ACP) in {ethanol (EtOH) (1) + propylene glycol (PG) (2) + water (3)} mixtures from 20.0 to 40.0 °C to expand the solubility database of this drug in mixed pharmaceutical solvents useful for designing high concentrated liquid products including injectable solutions. This is because ACP is an analgesic drug widely used available for oral administration as tablets or solutions. Besides, as injectable products, it is only available for perfusion in as 1 g in 100 mL (1.0%m/v). However, it is not available as 5 mL ampules for supplying doses of 500 mg. As demonstrated in this research some cosolvent mixtures allow ACP concentrations higher than 10.0%m/v, for instance the aqueous ternary mixture with 20% w/w of ethanol and 30% w/w of PG, among other possible mixtures. Flask shake method and UV–vis spectrophotometry were used for ACP solubility determinations at different temperatures. ACP solubility results are presented as Cartesian and triangular solubility profiles. ACP solubility increases with temperature arising and the cosolvent proportion in the mixtures. Maximum %m/v ACP solubility value is observed in the aqueous ethanol binary mixture of w1 = 0.80 at all temperatures being 21.18% at 25.0 °C. All the solubility values were well correlated using the Jouyban-Acree model obtaining mean percentage deviations of 3.8% (N = 330). In this way, %m/v equilibrium solubility of ACP in {EtOH + PG + water} mixtures has been studied and correlated at several temperatures as contribution to preformulation studies of injectable homogeneous liquid pharmaceutical dosage forms. [ABSTRACT FROM AUTHOR]

Scanning transitiometry is an important calorimetric method co-invented by Jean-Pierre E. Grolier and Stanisław L. Randzio. Transitiometry enables to measure highly sensitive under high-pressure and high-temperature conditions. Nowadays, process modelling is a tool of increasing importance beyond the process of understanding process dynamics. For a valid modelling approach, a reliable data base at process conditions is required. Many processes are carried out at high temperature and pressure. Under such harsh conditions, comparatively few methods can be applied and thus limited kinetic parameters are known. Therefore, extrapolated values from low-pressure data are often utilized. Transitiometry can reduce this data gap for thermophysical properties such as heat capacity, thermal expansion coefficient and isothermal compressibility. In this paper, an overview about the method evaluation to determine thermophysical properties under high pressure using transitiometry is given. Additionally, an oversight is provided of the investigation of the decomposition kinetics of peroxides and their mixtures as another application area of high-pressure calorimetry. [ABSTRACT FROM AUTHOR]

Densities of aqueous solutions of MnSO 4 , CoSO 4 , NiSO 4 and CuSO 4 have been measured by vibrating tube densimetry up to near-saturation concentrations over the temperature range 293.15 ≤ T / K ≤ 343.15 at 5 K intervals and at 0.1 MPa pressure. Apparent molar volumes, V ϕ , calculated from the densities revealed close similarities among all four electrolytes, with their V ϕ values essentially differing by constant concentration-independent addends for each salt at each temperature. It was found that there is an almost linear relationship between V ϕ (MSO 4 ,aq) and the M–O bond length of the hydrated cations obtained from structural studies. This relationship can be used to predict values of V ϕ (MSO 4 ,aq) for other sulfate salts over wide ranges of concentration and temperature, providing that the requisite structural data are available. Measurements of selected ternary, quaternary and quinary mixtures of these electrolytes at constant total concentrations showed that their V ϕ values almost always exhibit linear mixing (Young's rule) behavior at all temperatures investigated. This finding can be exploited to predict the volumetric properties of solutions containing complex mixtures of bivalent metal sulfates. [ABSTRACT FROM AUTHOR]

The heat capacity of different mixtures of terpenes (α-pinene, β-pinene, limonene oxide) and solvents (acetone, toluene, ethyl acetate) at atmospheric pressure (85.1 kPa atm in Medellin, Colombia) were measured using a microcalorimeter at several terpene molar fractions and from room temperature to a value close to the solvent boiling point. The mixtures analyzed were acetone + α-pinene from 298.15 to 323.15 K, toluene + limonene oxide and toluene + β-pinene from 298.15 to 358.15 K, and ethyl acetate + β-pinene between 298.15 and 338.15 K. These mixtures, at the selected temperature ranges, are used in fine chemical catalytic reactions. The experimental heat capacity values were fitted to polynomials as a function of temperature. Excess heat capacity was calculated with the measured molar heat capacity for all the mixtures, it decreased with temperature. Experimental uncertainty was less than 1.5% with a confidence level of 95% using k = 2. The experimental results were consistent, for example the heat capacity of ethyl acetate + β-pinene mixture increased as the temperature increased and decreased with the composition of the solvent; at 308.15 K the heat capacity decreased from 252.73 to 245.17 J mol−1 K−1 when solvent composition increased from 0.1546 to 0.2797 and at a solvent composition of 0.1546, heat capacity increased from 237.26 to 252.73 J·mol−1·K−1 when temperature increased from 298.15 to 308.15 K. [ABSTRACT FROM AUTHOR]

In the current study, intermolecular forces in the five binary associating systems containing formamide (FA) and normal alkanols (1-pentanol up to and 1-nonanol) at 293.15 K to 323.15 and atmospheric pressure were investigated. Experimental density and viscosity for binary fluids were measured, and values of excess functions were calculated. The findings indicate that increasing the alkyl chain length increases the excess molar volumes of binary mixtures. Furthermore, values of mutual diffusion coefficients D for the above mixtures were obtained from the experimental viscosities. The observed diffusion behavior for the binary mixtures was explained in terms of intermolecular interactions and structural effects in fluids. For the binary mixtures of formamide + 1-hexanol up to 1-nonanol, a miscibility gap was observed at different mole fractions. Values of density, viscosity, and mutual diffusion coefficients are new and have not been reported in scientific papers yet. [ABSTRACT FROM AUTHOR]

Equilibrium solubility of triclocarban (TCC) expressed in mole fraction in 1,4-dioxane and cyclohexane, as well, as in 19 {cyclohexane (1) + 1,4-dioxane (2)} mixtures, was determined at seven temperatures from T = (288.15 to 318.15) K. Logarithmic TCC solubility in these cosolvent mixtures was adequately correlated with a lineal bivariate equation as function of both the mixtures composition and temperature. Apparent thermodynamic quantities for the dissolution and mixing processes were computed by means of the van't Hoff and Gibbs equations observing endothermal and entropy-driven dissolution processes in all cases. The enthalpy–entropy compensation plot of apparent enthalpy vs. apparent Gibbs energy was linear exhibiting positive slope implying enthalpy-driving for TCC transfer from cyclohexane to 1,4-dioxane. Ultimately, by using the inverse Kirkwood–Buff integrals it is observed that TCC is preferentially solvated by cyclohexane molecules in 1,4-dioxane-rich mixtures but preferentially solvated by 1,4-dioxane molecules in cyclohexane-rich mixtures. [ABSTRACT FROM AUTHOR]

The vapor–liquid phase equilibrium (VLE) data for binary systems of neohexane + cyclopentane, neohexane + N,N-dimethylformamide (DMF), cyclopentane + DMF and ternary system of neohexane + cyclopentane + DMF were determined with a modified Rose still at 101.3 kPa, and all the binary data passed the Wisniak's test (D < 5), which accorded with the thermodynamic consistency. Three activity coefficient models namely, Wilson, NRTL and UNIQUAC were used to correlate VLE data and get binary interaction parameters, then the ternary VLE data of neohexane + cyclopentane + DMF were estimated based on these model parameters using Aspen Plus software. The estimation values of the three models agree well with the experimental data (σ(T) < 0.5 K). Moreover, the analysis of the effect of DMF on the vapor–liquid phase equilibrium shows that DMF can act as an effective extractant for the system studied. [ABSTRACT FROM AUTHOR]

Mixtures of sulfoxides with molecular solvents possess interesting physicochemical properties and may have applications in chemical synthesis. Hereby we confirm and rationalize the previously reported excellent miscibility of diethyl sulfoxide (DESO) with methanol (MeOH). By performing a comprehensive potential energy surface investigation we identified a global minimum for each system and a significant number of local minima described at the hybrid density functional level of theory. A strong 0.18 nm long hydrogen bond forming between the oxygen atom of DESO and the polarized hydrogen atom of MeOH was evidenced both via the structural and spectral analyses. Our results robustly explain negative deviations in the DESO–MeOH mixtures from ideal behavior and interpret the experimental observations with microscopic precision. [ABSTRACT FROM AUTHOR]

Conductance data of some higher homologues of quaternary ammonium salts, namely, tetrapentylammonium bromide (Pen4NBr), tetrahexylammonium bromide (Hex4NBr), and tetraheptylammonium bromide (Hep4NBr) in 2-butoxyethanol (1) + water (2) mixture with 0.20, 0.40 and 0.60 mass fraction of 2-butoxyethanol were reported at 298.15, 303.15, 308.15, and 313.15 K. The 1978 Fuoss conductance-concentration equation was used to analyze the measured experimental conductance data. The values of limiting molar conductance ( Λ 0 ), ionic association constant (KA) and the association diameter (R) were obtained from the analysis. The ionic contributions to the limiting molar conductances were estimated using tetrabutylammonium tetraphenylborate (Bu4NBPh4) as the "reference electrolyte". A weak electrostatic ion solvent interaction was observed for these three salts from their calculated KA and R values. The study also revealed that in all solvent compositions and experimental temperatures, these salts exist as free ions. The association constants of the electrolytes do not vary significantly as a function of temperature. However, as the temperature was increased or solvent compositions were changed, a noticeable variation in the single-ion conductivity values as well as Walden product for the ions were seen. [ABSTRACT FROM AUTHOR]

This study focuses on how the addition of a variety of primary alcohols (methanol to 1-dodecanol) influences the local structure of 1-butyl-3-methylimidazolium iodide (abbreviated [C4mim]I). We used Raman and UV–Vis spectroscopies to gain molecular-level information about the conformational change of C4mim+ cations and the iodide ions, as well as information about the alcohol (ROH) in [C4mim]I mixtures. We found that a unique local structure in which I 3 - is formed without the external addition of iodine is generated on the alcohol-rich mixtures when short alkyl-chain length alcohols are placed in [C4mim]I, where the formation reaction is very slow phenomenon. Furthermore, we propose a plausible mechanism for the peculiar behavior of primary alcohols in [C4mim]I: specifically, how longer alcohols up to 1-dodecanol can mix with [C4mim]I over the entire compositional range but the mixtures become completely insoluble for tridecanol and beyond. [ABSTRACT FROM AUTHOR]

The main aim of this work is to study phase equilibria, surface tension, and adsorption of water + amine mixtures. To achieve this aim, the surface tension was studied for following mixtures: water + monoethanolamine (MEA), water + diethanolamine (DEA), water + triethanolamine (TEA), water + n-methyldiethanolamine (MDEA), and water + 2-amino-2-methyl-1-propanol (AMP) in the temperature range of 298.15 K to 323.15 K. Peng–Robinson–Stryjek–Vera equation of state (PRSV-EOS) was used to model the phase equilibria of the binary mixtures. The binary interaction parameters were adjusted to the experimental information of the phase equilibria to correctly model the properties of the phase equilibria. The surface tension of all mixtures was calculated by using linear gradient theory (LGT) + PRSV-EOS, Shereshefsky model (SM), and Lamperski model (LM). LGT + PRSV-EOS as fitted approach correctly modeled the surface tension of the water + amine mixtures. Overall deviation for all the mixtures is 0.66%, and our results were better than those published in the literature. The surface tensions of binary mixtures were correlated by SM and excellent results were obtained. The average percent deviation in correlation of surface tension of studied mixtures was 2.2%. Based on Shereshefsky model, the standard Gibbs energy of adsorption ( Δ G o ) and the free energy change ( Δ G s ) in the surface region were calculated. The free energy change was used to obtain the excess number of molecular layers in the surface region. The magnitude of Δ G s and Δ G o was discussed in terms of nature and type of intermolecular interactions in binary mixtures. Additionally, the Lampersky model was used to predict the surface tension of studied mixtures and surface compositions. The surface compositions were used together with Shereshefsky model results to identify the adsorption of the amine at surface layer. [ABSTRACT FROM AUTHOR]

The cloud point temperature of poly(N-isopropylacrylamide) was measured in aqueous solutions containing salt mixtures. Solutions were made with SO 4 2 - , a strongly hydrated anion, I−, a weakly hydrated anion, or both anions together with a common alkali metal counterion: Li+, Na+, K+ or Cs+. Nonadditive behavior was observed when the MI concentration was increased in the presence of 0.2 mol⋅L−1 M2SO4. Although complex changes in the cloud point temperature were observed with all four metal counter cations, the magnitude of the effects differed substantially amongst them. More specifically, SO 4 2 - was able to attract cations away from I− in each case, but its propensity to do so depended on the relative strength of the cation–iodide versus the cation–sulfate interactions. When the counterion was stripped away from it, I− became more hydrated and acted more like a strongly hydrated anion. A competitive binding model was employed to determine the fraction of cations bound to SO 4 2 - in the presence of I−, allowing for a qualitative comparison of the fraction of strongly hydrated I− ions that was produced with all four cations. K+ showed the greatest relative affinity for SO 4 2 - . As such, experiments performed with this cation led to the greatest fraction of I− that was more hydrated and displayed the strongest nonadditive behavior. By contrast, Cs+ showed the weakest relative affinity for SO 4 2 - , resulting in the least pronounced nonadditivity. This work demonstrates that the identity of the counter cation plays a critical role in the nonadditive behavior of salt mixtures when both weakly and strongly hydrated anions are present. [ABSTRACT FROM AUTHOR]

The vapor–liquid phase equilibrium (VLE) data for binary systems of: n-hexane + methylcyclopentane, n-hexane + N-methylpyrrolidone (NMP), methylcyclopentane + NMP and ternary system of n-hexane + methylcyclopentane + NMP were determined with a modified Rose still at atmospheric pressure (101.3 kPa), and all the binary data passed the Wisniak area test and Van Ness point test, which accorded with the thermodynamic consistency. Three thermodynamic models Wilson, NRTL and UNIQUAC were used to correlate binary data and get binary interaction parameters, then the built-in parameters of the Aspen Plus software were replaced by the obtained model parameters to estimate the ternary data of n-hexane + methylcyclopentane + NMP. The estimation values of the three models are in good agreement with the experimental data. Moreover, the effect of NMP was analyzed, and it found to be an effective candidate extractant for the extractive distillation of n-hexane + methylcyclopentane. [ABSTRACT FROM AUTHOR]

Knowledge of the protonation constants of α-amino acids is important, interesting and necessary for complete understanding of the physiochemical behavior of the acids. The acid–base chemistry of zwitterionic compounds such as α-amino acids has been characterized in terms of the macroscopic constants; K1, K2; the microscopic constants; k11, k12, k21, k22 and the tautomeric constant; kz. The compounds may exist in four different microforms; a cation, zwitterion (dipolarion), neutral species and anion. In this study, both to demonstrate whether the predominant species are zwitterion or the neutral form and to predict the change of dipolar form to neutral form ratio in dioxane–water mixtures, the macroscopic protonation constants of the α-amino acids, glycine, DL-alanine, DL-valine, L-leucine, DL-phenylalanine and L-serine, and their esters, were determined potentiometrically using a combined pH electrode system calibrated as the concentration of hydrogen ion and later the microscopic and tautomeric constants of the amino acids were calculated in dioxane–water mixtures (20, 40, and 60% dioxane (v/v)). Titrations were performed at 25.0 ± 0.1 °C and the ionic strength of the medium was maintained at 0.10 mol·dm−3 using sodium chloride. The protonation constants were influenced by changes in solvent composition and the effects of solvent composition on the protonation constants are discussed. Also, the variation of microscopic constants and the ratio of zwitterionic form to neutral form are discussed on the basis of solute–solvent interactions of amino acids in dioxane–water mixtures. [ABSTRACT FROM AUTHOR]

Solubility of meloxicam in {methanol + water} mixtures from 293.15 to 313.15 K has been determined and correlated by means of the Jouyban–Acree model. By using the van't Hoff and Gibbs equations the respective apparent thermodynamic quantities for the dissolution and mixing processes, namely Gibbs energy, enthalpy, and entropy, were calculated. A non-linear enthalpy–entropy relationship was observed in the plot of enthalpy vs. Gibbs energy exhibiting negative but variable slopes in the composition region 0.00 < x1 < 0.60 and variable negative and positive slopes in the other mixtures. Based on the inverse Kirkwood–Buff integrals it follows that meloxicam is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by methanol molecules in mixtures 0.31 < x1 < 1.00. [ABSTRACT FROM AUTHOR]

Mixtures of ethylene glycol with water are a prominent example of media with variable viscosity, and ethylene glycol molecules serve as a prototype of various polyols having multiple hydroxyl groups. The dynamic viscosity of ethylene glycol–water mixtures was measured by vibro-viscosimetry over entire range of mole fraction under atmospheric pressure and from 10 to 30 °C; the variation of the viscosity activation energy with ethylene glycol mole fraction was determined and is discussed. In the present work we propose a novel equation for modeling the concentration dependences of the activation energy and viscosity. The theory is based on the assumption that the nonlinear characteristics can be associated with some structural changes of the mixtures, and that the reaction kinetics can be applied to this breakdown. The Grunberg–Nissan parameter and viscosity deviations were calculated. The possible changes in the variety of complexes for different concentration ranges is discussed. Correlation between the activation energy and pre-exponential factor was made. Three concentration regions are determined, separated by ethylene glycol molar fractions x = 0.11 and 0.43, where the structure of the water/ethylene glycol complexes changes. [ABSTRACT FROM AUTHOR]

This comparative study reports the measured liquid–liquid equilibrium (LLE) data and phase diagrams for the two ternary systems of {water + phosphoric acid + aryl alcohols (2-phenylethanol and 3-phenylpropanol)} at temperatures of (298.2, 308.2, and 318.2) K and atmospheric pressure (p = 0.1 MPa). Solubility data and mutual solubilities between the aryl alcohols and water were determined using turbidity measurements (cloud point titration method). Tie-line data were measured through acid–base titration and refractive index measurements. The results were validated through the Karl-Fischer titration method and mass balance calculations. The studied systems displayed Treybal's type-1 phase behavior, having one liquid pair that is partially miscible. The Othmer–Tobias correlation equation was applied to check the reliability of the tie lines. The experimental LLE data were correlated using the NRTL and UNIQUAC thermodynamic models, and the model binary interaction parameters between each pair of components were calculated. The results show the ability of these correlation models in representing the LLE data with acceptable average root-mean-square deviation (rmsd) values. As a result, the effect of temperature on the immiscibility region for the studied systems is small. For the studied systems, the separation factors are larger than unity, which means that the aryl alcohols have potential for separation of phosphoric acid from water. [ABSTRACT FROM AUTHOR]

The zwitterionic as well as solvophilic and solvophobic solvation behavior of DL-tyrosine, DL-leucine, DL-isoleucine and DL-threonine in aqueous and aqueous ethylene glycol systems have been studied at 298.15 K. For this study the solubilities of these amino acids in different solvent mixtures were measured at nine equidistant temperatures in the range of 278.15–318.15 K under 0.1 MPa pressure using the 'formol titrimetric' method. The order of experimentally found solubilities is DL-Thr > DL-Ile > DL-Leu > DL-Tyr. The standard transfer Gibbs energies, Δ G t 0 (i) , and entropies, T Δ S t 0 (i) of transfer were computed using the solubility data and are discussed. The observed Δ G t 0 (i) and T Δ S t 0 (i) versus composition profiles are in confusing order because of various interaction effects. The chemical effects of the transfer Gibbs energies Δ G t,ch 0 (i) and entropies of transfer values T Δ S t,ch 0 (i) have been obtained after removal of the cavity forming effect, dipole–dipole and dipole-induced-dipole interaction effects. The chemical contribution of these DL-amino acids are guided by the united effects of gradual change in the dispersion interaction, basicity and acidity, hydrogen bonding effects, solvophobic and solvophilic solvation of aqueous ethylene glycol as compared to those in the reference solvent, pure water. The solvophilic and solvophobic solvation effects of the transfer Gibbs energies, Δ G t,H1HbH 0 (i) , and entropies of transfer, T Δ S t,H1HbH 0 (i) , for the amino acids have been obtained after subtraction of the dispersion effect from the chemical transfer energies, which are guided by the side chains with amino acids. [ABSTRACT FROM AUTHOR]

In this article spectrophotometry is applied to measure the saturated solubility of some nucleobases in aquo-organic solvent mixtures of protic ethylene glycol at five equi-distant temperatures from 288.15 to 308.15 K under experimental pressure, p = 0.1 MPa. Standard Gibbs energies [ Δ G t ∘ (i) ] and entropies [ T Δ S t ∘ (i) ] of transfer from water to aqueous mixture of protic ethylene glycol have been evaluated at 298.15 K. The chemical contributions of these energetics [ Δ G t,chem ∘ (i) ] and [ T Δ S t,chem ∘ (i) ] of the involved nucleic acid bases have been computed by subtracting the cavity effect, dipole–dipole and dipole-induced dipole type interaction effects. The chemical composition of transfer energetics of nucleo bases is guided by different effects like dispersion interaction, basicity-acidity, hydrogen bonding, hydrophobic and hydrophilic interaction effects of aqueous ethylene glycol as compared to that of the reference solvent, water. The cavity effect has been estimated by using the Scaled Particle Theory. Computation of dipole–dipole and dipole-induced interactions has been performed using Keesom orientation expressions. The trend of variation of Gibbs energies due to chemical interactions are guided by decreased hydrophobic hydration (HbH), increased acidity and dispersion effects of aqueous ethylene glycol solvent mixtures as compared to the reference solvent, water. [ABSTRACT FROM AUTHOR]

The solubilities of etoricoxib (ETX), a COX-2 selective nonsteroidal anti-inflammatory drug, were determined in water–ethanol and ethanol–ethyl acetate mixtures at several temperatures (288.15–308.15 K). The solubility curves as a function of ethanol ratio were studied at five temperatures; they showed a single maximum located at 30% ethanol–ethyl acetate (δ1 = 19.70 MPa1/2). The measurements of the variation of inherent drug solubility with temperature were used to estimate different thermodynamic parameters, enthalpy, entropy and Gibbs energy of solution (ΔHS, ΔSS and Δ G hm S , respectively). The apparent enthalpies of solution were nonlinear functions of the ethanol ratio in aqueous mixture. Non-linear enthalpy–entropy compensation analysis was observed indicating different dissolution mechanisms with the variation in mixture composition. The solubility enhancement is entropy driven in water-rich (0–40% v/v ethanol) and enthalpy controlled in ethanol-rich (40–100% ethanol) compositions, likely due to water structure loss around nonpolar moieties of the drug and in the ethanol rich mixtures it is the enthalpy, probably due to the better drug solvation. [ABSTRACT FROM AUTHOR]

Solubility data for hesperetin in pure solvents and alcohol-rich regions of aqueous mixtures of methanol and ethanol were used to derive the solute descriptors for solubility prediction of hesperetin by using the Abraham solvation parameter model. Solubility data in aqueous mixtures of methanol and ethanol were analyzed by the linear solvation energy relationships approach to provide detailed insight into the solvent effect. In this regard, energy terms for solute–solvent and solvent–solvent interactions were defined in terms of dipolarity–polarizability, hydrogen bond basicity, hydrogen bond acidity and Hildebrand solvent parameter. Results indicate that the main contribution was from solvent–solvent interactions represented by the cavity term. Preferential solvation analysis was performed with the help of inverse Kirkwood–Buff integrals approach. Local composition and preferential solvation parameter were calculated as a function of mole fraction of methanol and ethanol. Results show that hesperetin is preferentially surrounded by water in water-rich regions, whereas methanol or ethanol are preferred in other compositions. This observation was discussed in terms of the solute hydrophobic hydration and specific hydrogen bonding interactions. [ABSTRACT FROM AUTHOR]

Diaminomethanal (an organic compound), was examined as entrainer for dehydration of isopropanol−water system by extractive distillation. Isobaric vapor−liquid equilibrium (VLE) data were studied for isopropanol−water−diaminomethanal system at 101.3 kPa, employing modified Othmer type still. The VLE data studied for the system comprising diaminomethanal were quite different from that of diaminomethanal-free system. The diaminomethanal represented a significant increase in the relative volatility of the isopropanol−water solution and led to termination of the azeotrope at a specific concentration. It was observed that the relative volatility for isopropanol−water mixture increases continuously with the increase in diaminomethanal concentration till 15.7 mol%. Results demonstrate that diaminomethanal is a functional entrainer for the separation of isopropanol−water mixture and 13 mol% of diaminomethanal concentration is enough to terminate the azeotrope. Furthermore, the experimental VLE data for ternary system were correlated by nonrandom two-liquid (NRTL) model and predicted values correlated with the experimental data very well. Further, the experimental data was verified for thermodynamic consistency by Wisniak–Tamir's modification of McDermott-Ellis and Wisniak's L-W thermodynamic consistency test. [ABSTRACT FROM AUTHOR]

The phase diagrams for carbamazepine (CBZ) and nicotinamide (NCT) in ethanol and ethanol/ethyl acetate mixture were constructed at 298.15 K and 313.15 K under atmospheric pressure using the static method. The solubility of the 1:1 cocrystal is correlated as a function of the cocrystal former (nicotinamide) concentration by a mathematical model based on solubility product theory and the complexation process. The phase diagram of a CBZ–NCT cocrystal in pure ethanol at 298.15 K is asymmetric, which leads to an excess of coformer being needed to isolate the cocrystal. In terms of this issue, it was found that the solvent mixture can have a significant effect on the symmetry of phase diagrams. Employing solvent mixtures could make the phase diagrams of the CBZ–NCT cocrystal more symmetric and enlarge the safe operation region for the cocrystal. Additionally, in the cocrystal formation process, the nucleation of cocrystal and carbamazepine in a slurry crystallization, is a competitive relationship. For avoiding single component crystallization, the supersaturation ratio of cocrystal to drug should be increased to inhibit carbamazepine nucleation. These findings are all beneficial to the development of the cocrystallization process of the CBZ–NCT cocrystal. [ABSTRACT FROM AUTHOR]

The aggregation behavior was investigated in mixtures of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) (anionic-rich catanionic) solutions. The study was conducted in solutions of water–ethylene glycol (EG) by means of surface tension, conductometry, cyclic voltammetry, zeta potential measurements, transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. The degree of counterion dissociation (α), critical micelle concentration, aggregation numbers, interfacial properties, interparticle interaction parameters, and morphology of aggregates were determined. Based on regular solution theory, the cosolvent effects between SDS and CTAB as surfactants were also analyzed for both mixed monolayers at mixed micelles (βM) and the air/liquid interface (βσ). It was shown that the formation of large aggregates occurred in the presence of an excess of anionic surfactant. A phase transition from cylindrical micelles to spherical micelles in the anionic-rich regime was observed with an increase in the EG volume fraction. The inter particle interactions were assessed in terms of cosolvent effects on the micellar surface charge density and the cylindrical-to-spherical morphology change. Zeta potential and size of the aggregates were determined using dynamic light scattering and confirmed the models suggested for the processes taking place in each system. [ABSTRACT FROM AUTHOR]

Enhanced oil recovery (EOR) has been one of the favorable methods in improving oil recovery and extending the production time. One of the techniques used in enhanced oil recovery (EOR) is gas flooding, because of the gases sweeping ability to displace the oil into the production well. Unfortunately, the gas injection method causes severe gas fingering because of the higher mobility and lower viscosity and density of the gas, compared to oil, which creates uneven fluid dispersion (fingering). Thus, a stabilized surfactant foam is introduced to control the injected gas mobility. This paper aims to characterize how the blends of non-anionic and anionic surfactants could act as foam stabilizing agents and to provide a brief exploration on their ability to improve the gas flooding process. The foamability and foam stability of single and mixed surfactant were tested at ambient and elevated temperature; additionally, a salt tolerance study was performed to identify the capability of the foam to withstand real reservoir conditions. Two anionic surfactants: sodium dodecyl sulphate (SDS) and alpha olefin sulfonate (AOS) and one non-ionic surfactant, octyl phenol ethoxylate (TX-100), were used in the study. Each single surfactant was tested for its viscosity and surface tension at the air/water interface under ambient conditions and compared with the mixed surfactants. Data has shown that blending of anionic and non-ionic surfactants has contributed to lower IFT compared to the individual surfactants and to increase viscosity, which is an early indicator of good foam stabilizer for foam flooding, which may lead to oil recovery improvement. The mixture of non-ionic and anionic surfactants, particularly TX-100 and AOS, showed better foamability and foam stability at elevated temperature than the individual pure surfactants. [ABSTRACT FROM AUTHOR]

The rate constant of the reaction of 2-chloroquinoxaline with piperidine was measured spectrophotometrically using different aqueous solutions containing DMSO or DMF. Whatever the experimental conditions used, this reaction follows pseudo first order kinetics and is not amine catalyzed. Furthermore, the second order rate constant, kA, increases with increasing percentage of DMSO in the solution, in contrast to DMF. The kA values were then correlated with solvent parameters α, β, π*, E T N and Y. Plots of log10kA against the reciprocal of the dielectric constant at 25 °C were found to be nonlinear in DMSO, while a linear relationship with a negative slope was found in the case of DMF. This difference between the solvents is presumably due to different solvation pathways between their initial and transition states. Thus, activation parameters ΔH#, ΔS# and ΔG# were evaluated and discussed to support this hypothesis. Finally, DFT calculations were performed, using the B3LYP functional and 6-311G(d,p) basis set, to determine optimum molecular geometry. IR, NMR spectra for both reactant and product and were then compared with experimental values. [ABSTRACT FROM AUTHOR]

The dissolution enthalpies ( Δ sol H m ) of dl-α-alanyl-dl-α-valine (AlaVal) and dl-α-alanyl-dl-α-norleucine (AlaNln) in aqueous solutions of dodecyl sulfate (SDS) at SDS concentration of mSDS = 0.05 mol·kg−1 and peptide concentration m = 0.010 to 0.025 mol·kg−1 at T = 298.15 K were measured via calorimetry. The results obtained have been used to calculate the transfer enthalpies ( Δ tr H m ) of AlaVal and AlaNln from water into (water + SDS) micellar solution. Thermochemical characteristics of the transfer of AlaVal, and AlaNln in the investigated range of peptide concentrations are compared. The results are interpreted by considering ion–ion, ion–polar, and hydrophobic–hydrophobic interactions between the dipeptides and SDS micelles. [ABSTRACT FROM AUTHOR]

1-Ethyl-3-methylimidazolium acetate (EMIMAc) is an ionic liquid (IL) often investigated as a solvent, especially in the context of biopolymers and biomass pretreatment. A reduced solvent efficacy occurs upon the addition even of low amounts of water to EMIMAc. Molecular mechanisms have not yet been fully understood. It is expected that the functionality as hydrogen bond donor and acceptor is key for the solvent–solute interactions. In this work, we analyze the solvent efficacy of EMIMAc in terms of hydrogen–deuterium (H/D) exchange at the C(2)-position in mixtures with water or acetic acid added as proton donors. Low-field NMR spectroscopy and deuterated solvents are used for a time-resolved evaluation of H/D exchange reactions. The H/D exchange is also modeled to explore changes in the reaction kinetics as a function of the mixture composition. The significant difference in calculated rate constant values among the concentration regimes shows that the chosen model equations of a possible pseudo-first-order and second-order reaction mechanism including water dissociation do not cover all interaction phenomena that influence the exchange in the individual concentration ranges. However, the modeling also indicates that the investigated interaction of EMIM + and Ac - remains constant for concentrated IL mixtures containing 70 mol % of EMIMAc in water up to diluted mixtures as low as 30 mol % EMIMAc. This exemplifies the change between ions strongly associated in networks in concentrated mixtures suitable for biomass pretreatment and the much less associated anion–cation pairs in diluted mixtures which leads to the decreased efficiency of EMIMAc with increasing water content. [ABSTRACT FROM AUTHOR]

A stricter definition of a deep eutectic solvent (DES) is urgent, so that it may become a sound basis for further developments in this field. This communication aims at contributing to deepening the understanding of eutectic and deep eutectic mixtures concerning their definition, thermodynamic nature and modelling. The glut of literature on DES applications should be followed by a similar effort to address the fundamental questions on their nature. This hopefully would contribute to correct some widespread misconceptions, and help to establish a stringent definition of what a DES is. DES are eutectic mixtures for which the eutectic point temperature should be lower to that of an ideal liquid mixture. To identify and characterize them, their phase diagrams should be known, in order to compare the real temperature depression to that predicted if ideality is assumed, and to define composition ranges for which they are in the liquid state at operating temperatures. It is also shown that hydrogen bonding between the DES components should not be used to define or characterize a DES, since this would describe many ideal mixtures. The future of deep eutectic solvents is quite promising, and we expect that this work will contribute to the efficient design and selection of the best DES for a given application, and to model properties and phase equilibria without which the process design is impractical. [ABSTRACT FROM AUTHOR]

Electrical conductances of solutions of tetraphenylphosphonium chloride, sodium tetraphenylborate, and sodium chloride in polyethylene glycol (PEG) + water mixed solvent systems having 0.200, 0.400, and 0.600 mass fractions of PEG are reported at 298.15 K. In this study three different average molar masses of PEG, e.g., 300 (designated as PEG 300), 400 (designated as PEG 400), and 600 (designated as PEG 600) g·mol−1 were employed. The conductance data have been analyzed using the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance, the association constant and the association diameter of the electrolytes. The ionic contributions to the limiting molar conductances have been estimated using tetraphenylphosphonium tetraphenylborate as the "reference electrolyte", considering the similarity of the sizes and chemical characters of the tetraphenylphosphonium and tetraphenylborate ions possessing a quasi-spherical surface of the phenyl rings. Analyses of the results provided important information as to the ion-association and solvation behavior of the electrolytes/ions investigated in PEG + water mixed solvent media. [ABSTRACT FROM AUTHOR]

The liquid–liquid equilibria (LLE) of the ternary system consisting of toluene, n-heptane, and ethylimidazolium bis(trifluoromethyl)sulfonylimide ([EtIM][NTf2]) were measured over the temperature range 298.2–313.2 K at ambient pressure. A binary mixture of [EtIM][NTf2] and methylimidazolium bis(trifluoromethyl)sulfonylimide ([MeIM][NTf2]) was used instead of [EtIM][NTf2] to investigate the effect of an additional ionic liquid on toluene separation from a toluene/n-heptane mixture. The LLE of a different ternary system of toluene, n-heptane, and [MeIM][NTf2] was also measured at 313.2 K and ambient pressure. Ionic liquids were not detected in the raffinate phase and thus no further separation unit for ionic liquids was required in the toluene separation process. The values of the distribution coefficient of toluene with the ionic liquids used in this study are higher than those with sulfolane at 313.2 K. This should provide a significant benefit because a higher distribution coefficient for toluene yields a more economic feed-to-solvent ratio in aromatic separations. [ABSTRACT FROM AUTHOR]

The effects of solvent properties on 1,1-diamino-2,2-dinitroethylene (FOX-7) solubility were investigated from the solubility values in aqueous co-solvent mixtures of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in terms of the linear solvation energy relationships with use of mathCAD software. For both aqueous mixtures, the main effect of hydrogen bond basicity was observed based on the solubility variation of FOX-7. The preferential solvation (the difference in composition between the solvation shell of the solute and the bulk composition in a mixture) of FOX-7 in the two aqueous of co-solvent solutions were investigated by using the method of inverse Kirkwood–Buff integrals (IKBI). The values of the preferential solvation parameters (δx1,3) were negative in water-rich mixtures, which are − 3.103×10−2 to − 2.936 × 10−2 for DMF (1) + water (2) mixtures and − 4.470 × 10−2 to − 3.995 × 10−2 for DMSO (1) + water (2) mixtures. However, in the co-solvent compositions ranging from 0.19 or 0.21 to 1 in mole fraction of DMF or DMSO, positive values of δx1,3 were observed. The preference of FOX-7 in water-rich mixtures can be explained based on the higher acidic behavior of FOX-7 molecules, which interact with the proton–acceptor functional groups of DMF and DMSO. KAT-LSER analysis showed that only the hydrogen-bond acceptor basicity of solvents played an important role on the FOX-7 solubility owing to its two amino functional groups. The squared correlation coefficient and F-statistic values are 0.98 and 314 for DMF + water mixture, and 0.96 and 130 for DMSO + water mixture, respectively. [ABSTRACT FROM AUTHOR]

The solubility and physicochemical properties, including density and refractive index in the ternary mixture solvent system (LiCl + CH3OH + H2O) at 298.15, 308.15 and 318.15 K were determined using the isothermal equilibrium method. Based on the experimental data, the phase diagrams and physicochemical properties versus composition diagrams at different temperatures were plotted and compared. It was found that the isothermal phase diagram at each temperature consists of one invariant point (LiCl + LiCl·H2O), two univariant curves and two crystalline regions corresponding to LiCl·H2O and LiCl, respectively. The densities and refractive indices in the ternary mixture solvent system at each temperature change regularly with the increase of LiCl concentration. The calculated densities and refractive indices at the three temperatures agree well with the experimental results. The salting-out rate of LiCl solution increases gradually with the increase of CH3OH concentration at each temperature. The results obtained in this work can be used to produce anhydrous LiCl at relatively low temperatures, even room temperature. [ABSTRACT FROM AUTHOR]

The densities (ρ) and viscosities (η) for the six binary mixtures of 1,6-dichlorohexane with cyclohexane, benzene, methylbenzene, 1,2-dimethylbenzene, 1,4-dimethylbenzene and 1,3,5-trimethylbenzene have been measured over the whole composition range and at 308.15, 313.15 and 318.15 K. The densities have been used to estimate the excess molar volumes (VE) of the binary mixtures at the three experimental temperatures. The experimental viscosities have been used to evaluate the deviations in viscosities (∆η) for the binary mixtures. The densities and viscosities increase as the mole fraction of 1,6-dichlorohexane increases in the binary mixtures. The excess molar volumes for the binary mixtures of 1,6-dichlorohexane with cyclohexane and with benzene are positive over the whole concentration range, at all the three experimental temperatures, while values for the binary mixtures of 1,6-dichlorohexane with methylbenzene, 1,2-dimethylbenzene, 1,4-dimethylbenzene, and 1,3,5-trimethylbenzene are negative for the entire composition range at the three experimental temperatures except for a positive value of VE at lower mole fractions of 1,6-dichlorohexane for the binary mixtures of 1,6-dichlorohexanes with 1,2-dimethylbenzene at 313.15 K. The ∆η values are negative for all the six binary mixtures at the three experimental temperatures. The experimental data of excess molar volumes VE and deviations in viscosities ∆η have been fitted using the Redlich-Kister polynomial equation. However, VE values for binary mixtures of 1,6-dichlorohexane with 1,2-dimethylbenzene at 313.15 K have been fitted using the Myers and Scott equation. The standard deviations in excess molar volumes [σ (VE)] and in deviations in viscosities [σ (∆η)] have also been evaluated. The experimental values of viscosities have been correlated with several equations suggested by Grunberg and Nissan, Katti and Chaudhri, and Hind, Mclaughlin and Ubbelohde. The Hind-Mclaughlin-Ubbelohde equation was found to be most suitable for the viscosities for all the binary mixtures studied at the three experimental temperatures. The results are discussed in terms of molecular interactions between the components of binary mixtures. [ABSTRACT FROM AUTHOR]

The solubilities of cefmetazole acid in methanol, ethanol, isopropanol and water were determined experimentally by using the saturation shake-flask method within the temperature range from (278.15 to 303.15) K under pressure p = 101.1 kPa. At a fixed temperature, the cefmetazole acid solubility falls in the order methanol > ethanol > isopropanol > water. The apparent dissolution enthalpy, dissolution entropy and Gibbs energy change were calculated. The acquired solubilities were correlated with Apelblat’s equation. The largest value of relative average deviation for mole fraction solubility was 0.45 × 10−2, and of root-mean-square deviation, 0.747 × 10−5. The type and extent and direction of solute-solvent interactions were identified using the concept of Linear Solvation Energy Relationship. In addition, the preferential solvation parameters (δx1,3) of cefmetazole acid in co-solvent mixtures of methanol (1) + water (2), ethanol (1) + water (2) and isopropanol (1) + water (2) were derived via the inverse Kirkwood-Buff integrals method. At 298.15 K, the magnitude of preferential solvation of cefmetazole acid by the co-solvent is highest in methanol mixtures, followed by ethanol mixtures, and finally by isopropanol mixtures. [ABSTRACT FROM AUTHOR]

The interaction of the antidepressant drug nortriptyline hydrochloride (NOT) with the surface-active ionic liquid (SAIL), 1-decyl-3-methylimidazolium chloride, [C10mim][Cl], has been studied using multiple techniques, including conductometric titration, tensiometric, fluorometric, dynamic light scattering and UV-visible spectrophotometric measurements. There is a significant decrease in the cmc of SAIL on the addition of the drug NOT, indicating adsorption of drug molecules in the outer portion of the micelle. In the present study, the values of the packing parameter, P, lie in the range of 0-0.3, which suggests that the micelles formed are spherical in nature. More negative values of the standard Gibbs energy of adsorption, ΔGad∘, compared to ΔGm∘ support our contention that adsorption of SAIL on the air-solution interface is relatively more favorable than its micellization in the presence of NOT. Fluorescence and DLS studies indicate that the aggregation number, Nagg, and hydrodynamic radius of SAIL increase with increase in concentration of NOT. The UV-visible spectroscopic study confirms the formation of a new complex between SAIL and NOT; this is also supported by the negative Gibbs energy of complexation. [ABSTRACT FROM AUTHOR]

The densities of binary and ternary mixtures of benzyl alcohol + ethyl butyrate and/or diethyl malonate were measured at T = (293.15-313.15) K and p = 0.087 MPa. From these data, the excess molar volumes, partial molar volumes, excess partial molar volumes, partial molar volumes at infinite dilution, thermal expansion coefficients and their excess values were calculated. The Redlich-Kister equations were fitted to the excess molar volumes data. The results show that the excess molar volumes for all considered binary and ternary systems are negative and decrease with increasing temperature. The same behavior was observed for the excess thermal expansion coefficients. Data for excess volumes in ternary system were fitted with the Nagata-Tamura and Cibulka models for which the Cibulka equation showed better fitting. The intermolecular interactions between molecules in these mixtures are discussed and explained based on these experimental data. [ABSTRACT FROM AUTHOR]

Mathematical modeling of physicochemical properties such as solubility is an interesting issue for drug discovery and development. Modeling and prediction of solubility in cosolvent + water mixtures can help in finding appropriate solvent mixtures without experiments. The solubility of drugs in ethanol + water mixtures (up to 50 % of cosolvent) is applied to develop a quantitative structure-property relationships (QSPR) model, by combination of the double log-log model and different descriptors. The prediction capability and the accuracy of the models were checked using statistical parameters and the leave-drug-out cross-validation method. The combined double log-log model with Abraham solvation parameters gives the best results (22.4 % overall mean percentage deviation). In addition, the prediction capability of the developed model was compared with previously reported models in the literature. The results confirm that the developed model in this study has an overall mean percentage deviation less than the ideal mixing (46.6 %) and log-linear (40.9 %) models. These results show that the combination of the double log-log model with computational Abraham solvation parameters is an acceptable model to predict solubility of drugs in ethanol + water mixtures up to 50 % of cosolvent ethanol. [ABSTRACT FROM AUTHOR]

Modeling of mineral reaction equilibria and aqueous-phase speciation of C-O-H fluids requires the dielectric constant of the fluid mixture, which is not known from experiment and is typically estimated by some rule for mixing pure component values. In order to evaluate different proposed mixing rules, we use molecular dynamics simulation to calculate the dielectric constant of a model HO-CO mixture at temperatures of 700 and 1000 K at pressures up to 3 GPa. We find that theoretically based mixing rules that depend on combining the molar polarizations of the pure fluids systematically overestimate the dielectric constant of the mixture, as would be expected for mixtures of nonpolar and strongly polar components. The commonly used semiempirical mixing rule due to Looyenga works well for this system at the lower pressures studied but somewhat underestimates the dielectric constant at higher pressures and densities, especially at the water-rich end of the composition range. [ABSTRACT FROM AUTHOR]

Densities ( ρ) have been measured from 298.15 to 313.15 K at atmospheric pressure over the entire composition range for binary mixtures of benzyl alcohol with 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene and tetrachloroethylene. Further, the speeds of sound in these mixtures were also measured from 303.15 to 313.15 K. The experimental density data were used to compute excess molar volumes ( V) which were compared with the Redlich-Kister and Hwang equations. Excess speeds of sound ( u), isentropic compressibilities ( κ) and excess isentropic compressibilities ( $$ \kappa_{S}^{\text{E}} $$ ) were evaluated from experimental speed of sound and density data. Moreover, the experimental speeds of sound were compared in terms of theoretical models proposed by Schaaff's collision factor theory and Jacobson's free length theory. The experimental and derived properties are discussed in terms of intermolecular interactions between component molecules. [ABSTRACT FROM AUTHOR]

Refractive indices of ternary mixtures of water + methanol + (ethanol or propan-1-ol), (water or methanol) + ethanol + propan-1-ol and their binary mixtures have been measured at 293.15 K and at atmospheric pressure over the whole composition range. The refractive index deviations were calculated and fitted to the Redlich-Kister equation for binary mixtures, and the Cibulka equation for ternary mixtures. Furthermore, we demonstrate that the refractive index of the associated ternary mixtures can be estimated with relative errors from 0.036 to 0.861 % by using the several mixing rules and the refractive indices of the corresponding pure components. The behavior of refractive indices is associated with solvent-solvent interactions and the formation of clusters. [ABSTRACT FROM AUTHOR]

The density $$ \rho_{23} $$ and $$ \rho_{123} $$ and speed of sound $$ u_{23} $$ and $$ u_{123} $$ data of benzene (2) + o- or m- or p-chlorotoluene (3) binary and ternary mixtures and 1-methylpyrrolidin-2-one (1) + benzene (2) + o- or m- or p-chlorotoluene (3) mixtures have been measured over the entire composition range at 293.15, 298.15, 303.15 and 308.15 K. The experimental densities and speeds of sound have been utilized to evaluate excess molar volumes, $$ V_{23}^{{\text E}} $$ and $$ V_{123}^{{\text E}} $$ , and excess isentropic compressibilities, $$ \kappa_{{{S,{\text 23}}}}^{{\text E}} $$ , $$ \kappa_{{{S,{\text 123}}}}^{{\text E}} $$ , of the studied binary and ternary mixtures. The results indicate that $$ V_{23}^{{\text E}} $$ for benzene (2) + o- or m- or p-chlorotoluene (3) mixtures are positive and $$ \kappa_{{{S,{\text 23}}}}^{{\text E}} $$ are negative over full range of composition. Further, $$ V_{123}^{{\text E}} $$ and $$ \kappa_{{{S,123}}}^{{\text E}} $$ of 1-methylpyrrolidin-2-one (1) + benzene (2) + o- or m- or p-chlorotoluene (3) mixtures are negative over entire composition range. The $$ V_{23}^{{\text E}} $$ , $$ V_{123}^{{\text E}} $$ and $$ \kappa_{{{S,{\text 23}}}}^{{\text E}} $$ , $$ \kappa_{{{S,{\text 123}}}}^{{\text E}} $$ data have been analyzed in terms of Graph and Prigogine-Flory-Patterson theories. The $$ V_{23}^{{\text E}} $$ , $$ V_{123}^{{\text E}} $$ data have also been analyzed in terms of Sanchez and Lacombe theory. It has been observed that Graph theory correctly predicts the sign and magnitude of the excess molar volumes and excess isentropic compressibilities of the present binary and ternary mixtures. [ABSTRACT FROM AUTHOR]

The pVT-properties of water + n-pentane and water + n-hexane mixtures in temperature intervals from 305 to 542 K and pressures up to 15 MPa were measured in a constant-volume piezometer. The line of phase equilibrium hydrocarbon-vapor with water and their critical parameters were determined. Critical temperatures and pressures are constant and close to 0.9 mol fraction of water, remaining the same as for the upper critical end-point, while the densities increase. All critical parameters decrease above 0.93 mol fraction of water. The common three-phase lines for measured systems are presented. [ABSTRACT FROM AUTHOR]

Chemical thermodynamics is of central importance in chemistry, physics, the biosciences and engineering. It is a highly formalized scientific discipline of enormous generality, providing a mathematical framework of equations (and a few inequalities), which yields exact relations between macroscopically observable thermodynamic equilibrium properties of matter and restricts the course of any natural process. While these aspects alone are already of the greatest value for practical applications, in conjunction with judicially selected molecular-based models of material behavior, that is to say by using concepts from statistical mechanics, experimentally determined thermodynamic quantities contribute decisively towards a better understanding of molecular interactions and hence of real macroscopic systems. A plenary lecture affords the lecturer an opportunity to survey a few reasonably large sub-areas of the fields he works/worked in and to reflect on them from the perspective of many years of research. The general subject I selected for this review, i.e. chemical thermodynamics of liquid nonelectrolytes (pure or mixed), is vast. Over the last decades, the field's impressive growth has been stimulated by the continuously increasing need for thermophysical property data and phase equilibrium data in the applied sciences, and it has greatly profited by advances in experimental techniques, by advances in the theory of liquids in general, and by advances in computer simulations of reasonably realistic model systems in particular. Specifically, I shall focus on just three topics of increasing complexity: (1) heat capacities and related quantities of fairly simple molecular liquids, predominantly at or near orthobaric conditions; (2) chemical thermodynamics of binary liquid mixtures containing one strongly dipolar aprotic component; (3) caloric properties of dilute solutions of nonelectrolytes, with emphasis on properties of aqueous solutions at infinite dilution (which are of importance in biophysical chemistry). [ABSTRACT FROM AUTHOR]

Excess molar volumes V for 40 mixtures of heptane with a liquid alkane and apparent molar volumes in heptane for eight solid alkanes have been obtained at 298.15 K. They include five linear, 30 branched-chain, and 13 cyclic alkanes. Almost all systems exhibit negative V values. For mixtures with open chain alkanes, V increases from C5 to C7 and then decreases. A similar trend is shown by mixtures with cycloalkanes. V values are compared with known H data for mixtures with heptane and tetrachloromethane. Signs and trends of V and H are correlated with the free volume and interactional terms of the Flory theory. The partial molar volumes at infinite dilution in heptane, V°, have also been obtained and discussed together with literature data on other hydrocarbons and polar compounds. The calculated contributions to V° by CH, CH, CH and C groups are compared with previously determined contributions of polar groups. The lower contributions of the latter groups are explained with the volume contraction caused by dipole-induced dipole interaction. The volume effects associated with branching and cyclization have been evaluated and compared with the corresponding effects on solvation enthalpy. The branching effect, in the order of magnitude of few cm·mol, and the larger negative values of cyclization volumes, down to −24 cm·mol, are discussed in terms of packing and solute-solvent interactions, in analogy to polar organic solutes either in heptane and tetrachloromethane. A negative cyclization effect is also exhibited by the solvation enthalpies. [ABSTRACT FROM AUTHOR]

Densities and speeds of sound for binary mixtures of diethylene glycol monomethyl ether and triethylene glycol monomethyl ether with 3-methyl-1-butanol and 2-methyl-2-butanol were measured at 288.15, 298.15 and 308.15 K, over the entire range of compositions at atmospheric pressure, using an Anton Paar DSA 5000 density meter. The experimental densities and speeds of sound have been used to calculate excess molar volumes and excess molar isentropic compressibilities. The speed of sound data are compared with theoretical speeds of sound calculated using several approaches. [ABSTRACT FROM AUTHOR]

The densities, ρ, and speeds of sound, u, of ternary o-toluidine (OT, 1) + tetrahydropyran (THP, 2) + pyridine (Py) or benzene or toluene (3) mixtures have been measured as a function of composition at 298.15, 303.15 and 308.15 K. Values of the excess molar volumes, $$ V_{123}^{\text{E}} , $$ and excess isentropic compressibilities, $$ (\kappa_{\text{S}}^{\text{E}} )_{123} , $$ of the studied mixtures have been determined by employing the measured experimental data. The observed thermodynamic properties were fitted with the Redlich-Kister equation to determine adjustable ternary parameters and standard deviations. The $$ V_{123}^{\text{E}} $$ and $$ (\kappa_{\text{S}}^{\text{E}} )_{123} $$ values were also analyzed in terms of Graph theory. It was observed that Graph theory correctly predicts the sign as well as magnitude of $$ V_{123}^{\text{E}} $$ and $$ (\kappa_{\text{S}}^{\text{E}} )_{123} $$ values of the investigated mixtures. Analysis of the data suggests strong interactions and a more close packed arrangement in OT (1) + THP (2) + Py (3) mixtures as compared to those of the OT (1) + THP (2) + benzene (3) or toluene (3) mixtures. This may be due to the presence of a nitrogen atom in Py which results in stronger interactions for the OT:THP molecular entity as compared to those with benzene or toluene. [ABSTRACT FROM AUTHOR]

The protonation constants of some α-amino acids (glycine (Gly), l-alanine (Ala), l-valine (Val), l-serine (Ser), l-leucine (Leu) and l-isoleucine (Ile)) were studied in water and DMSO-water solution mixtures containing 30, 50 and 70 vol-% DMSO; in addition the complex formation equilibria of their copper(II) complexes were studied by potentiometric technique using a combined pH electrode system calibrated in concentration units of the hydrogen ion at 25 ± 0.1 °C under a nitrogen atmosphere, and at an ionic strength of 0.10 mol·dm NaNO. The protonation constants and the overall stability constants of copper(II) complexes were influenced by changes in solvent composition, and their variations are discussed in terms of solvent and structural properties. [ABSTRACT FROM AUTHOR]